Dual role port automatic role reversal prevention

A system, comprising:

• a power bank configured to operate as a source device, the power bank comprising:
• a battery;
• a dual-role bus voltage terminal for transferring power to the battery and from the battery;
• and
• a micro-processing unit configured to:
• control the battery to source power to a sink device via the dual-role bus voltage terminal when the battery includes a first amount of stored energy;
• and
• inhibit power transfer from the sink device to the battery via the dual-role port when the battery includes less energy than the first amount of stored energy.

A tangible non-transitory computer readable storage medium that comprises instructions, which when implemented by a micro-processing unit, cause the micro-processing unit to:

• cause a device communicatively coupled to the micro-processing unit to receive power from a source device via a dual-role port capable of non-concurrent operation as both an input terminal and an output terminal, the source device having terminated a communication channel coupling the source device and the dual-role port with a pull-up signal at a source side of the communication channel while the source device is outputting power;
• detect removal of the pull-up signal at the source side of the communication channel;
• begin a timer when the removal of the pull-up signal is detected;
• detect a pull-down signal terminating the communication at the source side of the communication channel;
• and
• inhibit a transfer of power to the source device via the dual-role port when the pull-down signal terminating the communication at the source side of the communication channel is detected prior to expiration of the timer.